In hydraulic fracturing operations proppants coated with resin are used to enhance their crush strength, chemical resistance, and proppant flowback control. The majority of resin coated proppants are prepared using phenol-formaldehyde resin (Novolac) hardened with hexamine at an elevated temperature in a dedicated plant setting. The objective of this study is to disclose a simple method to coat proppant at ambient temperature to provide free flowing curable and pre-cured proppant without loss of any performance.<br/>In this work, a free-flowing resin coated proppant was prepared by coating silica substrate with a combination of resin chemicals. The coating was crosslinked with other components to produce either of pre-cured or curable coating. In some cases, diluents were mixed to adjust the viscosity of resins, and for an efficient and uniform coating on to the sand grains. Reinforcement of the resin coating with carbon nanotube was also studied. Coated sand was evaluated for particle size distribution, thermal resistance and fluid compatibility, API proppant crush resistance strength, and API long-term conductivity. Microscopy was used to ascertain the full dispersion of nanomaterial in the resin.<br/>Liquid resin used for coating sand was diluted with reactive diluents to adjust its viscosity suitable for mixing at definite batch size. Different kinds and combination of catalyst and alcohols were employed for the optimum curing and hardening of the resin. The free-flowing resin coated sand was prepared from resin efficiently by employing the catalyst accelerator that will be economical when scaled up to industrial scale. The properties of the fully cured coated sand indicated that the prepared coating is suitable for use in oilfield applications. Dilution of resin with reactive diluents helped in the uniform dispersibility of nanotubes in the resin as determined by microscopy. API long-term proppant pack conductivity showed improvement in the strength of the coated sand.

Method to produce resin coated proppants at ambient temperature for hydraulic fracturing

ACS Fall 2021

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